Process of producing concentrated formic acid from formates.



UNITED STATES PATENT oFFIoE.

EMIL FRANKIE, OF GRUNAU, NEAR BERLIN, GERMANY, ASSIGNOR TO CHEMISOHEFABRIK GRUNAU LANDSHOFF & MEYER AKTIENGE- SELLSOHAFT MANUFACTURINGCHEMISTS, OF GRUNAU, NEAR BER- LIN, GERMANY.

PROCESS OF PRODUCING CONCENTRATED FCRMIC ACID FROM FQRMATES.

Specification of Letters PMGIW.

Patented June 18, 1907.

Application and Jun027,1906. Serial N0.323,687.

To all whom it may concern:

Be it known that I, Dr. EMIL FRANKE, a subject of the King of Prussia,and a resident at (.iriinau, near Berlin, Germany, have invented anImproved Process for Producing Concentrated Formic Acid from Formates,of which thefollowing is a specification.

The present invention relates toand has for its object an improvedprocess for pro ducing concentrated formic acid from for mates.

in ihicomposing a formate by means of a rather powerful acid,decomposition of the formic acid takesplace to a certain extent. Forexample, in heating format-e of soda with concentrated sulfuric acid upto 45 .per cent. of the formic acid is lost, and with 90 per cent.phosphoric acid up to 35 per cent. is lost. For this reason it hashitherto been possible to only make somewhat weak formic acid of about(it) to per cent. proportion of acid, rather weak sulfuric acid and dampformatc having been used. The French pat cnt specification 341,764 madeknown a i'nethod by which it was also )ossible to 01m ploy highlyconcentrated sulfuric acid for decomposing formatcs and thus to makehighly concentratedformic acid. The characteristic feature of thatmethod consists in dissolving or intimately mixing the formates inci'mccntrated formic acid and then adding sulfuric acid to this mixture.Instead of sulfuric acid, iii-sulfate of soda can be used in preciselythe same manner, i. c. after mixing the formate with concentrated formicacid, the sulfuric acid in this sulfate acting analogously to thesulfuric acid.

Now the observation has been made that acid salts, for example, sodiumiii-sulfate.

may be allowed to act directly on formatc of l soda without previousmixture of the same with formic acid, without fearing decomposition ofthe formic acid. Comparative oxperimcnts as to the decomposition of dryfo-rinate of soda with concentrated sulfuric acid, of a mixture offormic acid and formatc of soda with concentrated sulfuric acid, and ofdry forn'iate of soda with bisulfatc of soda pcnscd with.

gave the following results in the same order, 1. (2.: 60.9, 128.5 and132.6 grams of formic acid (100 per cent.) were obtained from 200 gramsof formate (100 per cent), i. e. 45 per cent, 95 per cent, and 98 percent. yield were obtained. From this it is clearly seen that by usingsodium bisulfate a previous mixing of the formate with formic acid maybe omitted, without fearing a diminished yield.

The following is a suitable method of earrying out .thedecomposition:.100 parts of commercial formate of soda are intimatelymixed with 200 parts of finely owdered sodium bisulfate per cent.) anthe mixture is heated in a retort, said retort being preferably providedwith a stirrer. Formicacid of 974% per cent. concentration disti'lsover. A quite loose powder of anhydrous sodium sulfate remains behind inthe retort, on account of which a stirrer may be dislhis advantageousissue of the reaction was not to be seen forthwith, as thecontaininations accompanying commercial bisulfatc could easily have aninconvenient or troublesome cil'cet, especially Without previous mixingwith formic acid.

1- claim:

1. A process for producing concentrated formic acid from formate,consisting in intimatcly mixing a solid formate with the solid acid saltof a polybesic acid which is stronger than formic acid, and insubmitting the mixture thus formed to distillation.

2. A process for producing concentrated formic acid from formatcs,consisting in intimately mixing a solid formatc with the solid acid saltof a polybasic acid which is stronger than formic acid, and insubmitting the mixture thus formed to distillation in a retort, wherebysaid formic acid is distilled off.

3. A process for producing concentrated formic acid from formates,consisting in intimately mixing a solid fonnate with sodium bisulfate,and in submitting the mixture thus formed to distillation.

4. A process for producing concentrated formic acid from formates,consisting in inti- Inately mixing a solid formate with the acid InWitness whereof I have hereunto sighed salt'of a polybasic acid which isstronger than my name this 15th day of June, 1906, in the formic acid,and in submitting the mixture presence of two subscribing Witnesses.thus formed to distillatienin a; retort and in EMIL FRANKE. stirring thesame dur li distillation, whereby Witnesses:

'said formic acid is distllledv 06, substantially PAUL F. lViiEYER,

as described VVALTER SAECHTLING.

